As used herein the term “PV module” identifies a photovoltaic power generating unit in the form of an integrated structure comprising a plurality of electrically interconnected photovoltaic cells and means for supporting and protecting the cells, and the term “PV module assembly” identifies a structure comprising two or more PV modules that are mechanically ganged together and electrically interconnected to form a unitary power source. A variety of systems and methods have been devised for mounting PV modules and associated components of solar electric (PV) power generating systems on buildings. The market for solar electric power generating systems that operate in parallel with existing grid electricity supply and that can be safely and simply installed on the rooftops of businesses, factories, schools, hospitals, commercial establishments and the like, is growing rapidly in the United States and elsewhere. As the cost per watt has dropped in recent years for photovoltaic units, the need for improving methods of mounting photovoltaic modules to building roofs has become more critical. More precisely, as the cost of solar cells per se has declined, the non-solar cell components required for installing a functioning photovoltaic system become more critical with respect to overall system costs. However, care must be taken to insure that photovoltaic systems are installed with due respect to environmental factors such as wind-loading and environmental stresses, and preserving building integrity, notably, avoiding the use of mechanical fasteners that penetrate the roof.
A number of different approaches have been taken with respect to providing means for supporting photovoltaic panels on a roof. These prior methods are exemplified by the inventions described in U.S. Pat. No. 4,886,554, issued 12 Dec. 1989 to Woodring et al for “Solar Roofing Assembly”; U.S. Pat. No. 5,746,839, issued 5 May 1998 to Thomas L. Dinwoodie for “Lightweight, Self-Ballastng Photovoltaic Roofing Assembly”; and U.S. Pat. No. 6,148,570, issued 21 Nov. 2000 to Thomas L. Dinwoodie et al for “Photovoltaic Building Assembly With Continuous Insulation Layer”.
U.S. Pat. No. 6,148,570 discloses a photovoltaic building assembly comprising the use of a plurality of PV module support assemblies to support photovoltaic modules in close proximity to one another on a roof or other building support surface on which the photovoltaic building assembly is installed. Each of the PV module support assemblies comprises a base located on the building support surface, and an outwardly extending portion that projects through a continuous insulation layer, preferably in the form of a sprayed-on foam insulation layer, that covers the building support surface and the base of the PV module support assembly. The PV modules are mounted to and supported by the outwardly extending portions of the module support assemblies above the insulation layer. The base of the PV module support assembly may be made of concrete pavers or other heavy material to help counteract wind-induced uplift and sliding forces by their weight alone. U.S. Pat. No. 6,148,570 also teaches that by having their bases embedded within the insulation layer, and also by being fastened to the building support surfaces by adhesive or through the use of mechanical fasteners which may, or may not penetrate the building support surface, additional stability and mounting strength is achieved. The patent also suggests that the base portions may be sized so that embedding them within the insulation layer may be all that is needed to secure the PV module support assemblies to the building support surface. A characterizing aspect of the photovoltaic building assembly disclosed in U.S. Pat. No. 6,148,570 is that each PV module support assembly extends horizontally parallel to and in supporting relation to the mutually confronting edges of two adjacent modules, with each side of each module being supported by a different PV module assembly and adjacent modules being close to one another so as to form a covering for the supporting roof structure.